So the oven is getting heavy and in order to conserve weight i went with o60 – 16 gauge cold rolled sheet for the roof. The only problem is that it needs to be supported… and supported some more… A quick day turned into another long day with a lot of pieces of metal to cut and weld in place…I used the plasma cutter to cut the end caps then welded those in place. In making the ribs, I made one that i liked then matched the rest.
The exterior baking doors have so many pieces to them and so many roles… These doors need to keep the heat in but as i learned when i tossed an entire pallet into the oven, they regulate the air…very important unless you like seeing flame coming out the top of the chimney. You can get a fire going and fill it with wood and then walk away. A nice regulated burn results. I am not sure how to calculate the size of the vent… this was a guess as a few things have been along the way. These doors will also serve as a redundancy for retaining steam when baking. Turtle Rock Masonry has an insulated door with a vent door in it… This is my version. I used a rigid insulation from chiz brothers in pittsburg – very reasonable in price and perfect for this application.
Sorry about the lousy image quality…a ring fell off the camera and i ignored it…so i got a bunch of light bleeding into the exposure…grrr.. Need to reach the damper from the outside so that meant an extension…and yes i walked into the pointy end of my temporary damper handle…modified the exterior hearth so that just a clean frame sticks proud of the back surface… the gauges were inserted from the interior side to make them cleaner looking..then finally to cap all the mess…
Rear cap all in place… gauges semi installed…damper extension and insulation re-installed
Insulation is a nasty business…wear a respirator, eye glasses and cover all skin….and you will still be itchy at the end of it…Cold shower after helps to tighten the pores and keep the insulation from burrowing in…UGGH. So this is good quality insulation 8 lb. 2 inch thick. The thickness does not matter much…but the thicker the insulation the fewer pieces you handle. I used a kitchen knife (serrated are the best) and a straight edge to make the cuts…worked great. A frame wraps around the entire oven held up by gussets and a couple of cross braces. This frame will support the insulation and the side panels. Side panels were welded from the inside to keep the look clean and the bottom edge of the metal .060 slips over and registers to the bottom edge of the frame. The idea being to limit the amount of water that might get inside. This metal shell allows me to start using the oven.
More refractory material KS4V-plus… had some extra and thought a bit more mass on top of the brick would be good for strengthening the arch… now the arch and the hearth have equal amounts of material. Foil first..the concrete vibrator allows the material to settle and so pushes the air captured to the surface. Enough material for a healthy inch thick cap.
Ready for welding. The baking door is fully encased on the bottom half making it mostly air tight. The outer hearth will frame the outer doors and protrude through the rear wall. The patches are from a fix i needed to make to ensure that the door moves freely.
2 inch square stock guides the 1.75 inch steel rod counter weights…the stainless steel .060 thick flap doors were cut with a jump shear… the door is slightly heavier than the counter weights so will drift down if not set with the latch pins. The final version has 3/32 cable to prevent it from jumping off the pulley wheel. Also note that on the lower half there is a plate that will serve to encase the door when it is in the down position.
So a couple of things need to happen with this baking door… the spring loaded hinges need to be strong enough to lift the .060 stainless steel doors but not so strong that they do not open easily… mc master-carr had the perfect ones… these are stainless steel – 1.5 by 5.5 inch each… then the door needs to rise and fall easily… and not bind.. and when in the down position match up with the hearth so that ash and other burning matter does not fall down. So the pulley above is from an old sash window – i think. The frame of the door is 3/4 inch. In order to make a guide for the door i cut one side off of a 1″ square tubing – making a “U” shape profile. This allows the door to slide up and down and a little bit right and left but none front to back…simply it keeps the door captured. I also welded on another section of 3/4 square tubing to the sides of the door frame so that the door would not get caught up in the 1″ guide….(someone out there will care i am describing this). The metal piece with the counter sink, that has the cable disappearing into it… that is the hearth insert that makes the hearth continuous when the baking door is down and not in use.
The idea of the baking door is something i came across at Turtle Rock Masonry – they have made a number of different doors but i think that this one is really clever..the idea – at least what i can gather is that they make a pair of doors… one for firing and one for baking.. How they made them i have no idea so what follows is my version… Given that the oven will be mobile, I want my baking door to be present when i need it and then hidden away. Given all of the insulation and the height of the hearth meant that i had space for the door to drop down out of the way when not in use and to be lifted into place when the time for baking arrived. I also wanted the transition from the passive to the active position to be easy. My friend Sam reminded me to use the counterweight idea we had talked about….With a lot of things it’s easy to not like something but imagining what you like is a bit harder…i built and tore the door apart at least three times before i got what i wanted…and of course this is totally speculative… will it work…
Casting the chimney and setting in the dura-vent anchor plate… i had to cut the anchor plate in order to insert the concrete vibrator… super important note the viscosity of the refractory mortar and the stainless steel needles.
The damper was welded to the frame that contained the first casting. Using 14 gauge steel and a plasma cutter, I cut the parts of the chimney frame and welded it up including a notch to accommodate the extension of the damper. Inserted the foam plug into the damper to keep the casting where i want it and double stick tape to keep the negative space of the flue in place.
The chimney ends with an off the shelf dura-vent chimney pipe but to get to that i need to make a transition from the rectangular flue to an 8 inch diameter circle. Using the 3d cad program Rhino i drew the object and then outputted that to the CNC router for milling – a great transition over the course of 6 inches. The wood around the foam matches the profile of the underside of the damper that will then be welded into place. The wood frame keeps everything open and insures i get a good casting.
I had a complicated damper system all thought out and then decided to go with something simpler… old school kiln style damper… using 3/8 inch thick metal for the frame and the damper insert… hoping that this will endure the heat okay… so many calculated guesses in all of this… The idea with this is to ensure that the steam generated by the dough stays contained in the oven’s atmosphere.
Lots of bricks from Harbison and Walker – and insulation – Chiz Brothers very high compressive strength and great insulation -
platform required rethinking by the time i returned to california
the platform for the oven -